A major growing industry over the past decade has been the employment of synthetic elastomeric fibers in the manufacture of elastomeric yarns. Elastomeric yarns are used primarily in foundation garments, swim suits, and support hoisery. The primary function of the elastic yarn in these applications is to exert back-stress, when stretched wherein the back-stress is called holding power. A satisfactory elastomeric yarn must retain its holding power over long periods of extension and after repeated extension and relaxation. The properties of the elastomeric yarn should not significantly deteriorate in fabric dying or on repeated laundering. The discoloration under UV or sunlight should also be minimal.
A polyurethane resin, Spandex, manufactured by E. I. DuPont de Nemours and Co., represents the major synthetic elastomeric polymer being employed in the manufacturing of elastomeric yarns. Spandex is wet or dry spun into fibers by dissolving the Spandex in a relatively high cost solvent such as dimethyl acetamide or dimethyl formamide. The compositions of the present invention employ less costly mixed solvent systems such as a mixture of xylene and methanol. Furthermore, the raw material cost of Spandex can be several fold that of the raw material of the compositions of the present invention. Additionally, the compositions of the present invention exhibit improved versatility in a spinning operation as compared to Spandex. Recently, a new class of sulfonated elastomeric polymers has been described in a number of U.S. Pat. Nos. 3,642,728; 3,836,511; 3,870,841 and 3,847,854 herein incorporated by reference. These types of sulfonated elastomeric polymers constitute the general class of the compositions of the present instant invention. The aforementioned patents fail to clearly recognize or even imply the use of these types of polymers in a solution form for the manufacture of improved elastomeric fibers, but rather teach compositions of matter useful primarily in hot melt extrusion or molding type processes.